1. Field of the Invention
The present invention relates to a cleaning unit for removing toner from the surface of a photoconductive drum after image transfer to clean the photoconductive drum.
2. Description of Related Arts
Conventional cleaning units of this type include a cleaning chamber where toner is scraped away from the surface of a photoconductive drum, and a toner storage for storing therein the scraped toner, both of which are accommodated in a single unit thereof.
In the cleaning unit, typically, the toner adhering on the periphery of the photoconductive drum is scraped away by means of a blade slidably contacting the photoconductive drum, and transported to the toner storage by means of a rotative transportation roller and transportation paddle.
However, the toner, paper dust and the like adhering on the surface of the photoconductive drum cannot assuredly be scraped away with the aforesaid blade alone. Therefore, the conventional cleaning unit cannot ensure a sufficient cleaning performance and, hence, cannot provide a desirable image-transferring capability.
To this end, there has been proposed a cleaning unit having a cleaning roller for assisting a blade to scrape away toner as shown in FIG. 3. Referring to FIG. 3, the cleaning unit includes a cleaning chamber 901 where toner is scraped away from the surface of a photoconductive drum 904 and a toner storage 902 for storing therein the scraped toner, which are separated by a separator plate 903.
In this cleaning unit, a blade 905 slidably contacting the periphery of the photoconductive drum 904 is adapted to scrape the toner away from the periphery of the photoconductive drum 904 into the cleaning chamber 901. A cleaning roller 906 disposed below the blade 905 slidably contacts the periphery of the photoconductive drum 904 and rotates in association with the rotation of the photoconductive drum 904. The cleaning roller 906 serves to displace, on the periphery of the photoconductive drum 904, the toner and paper dust adhering thereon, so that the toner and paper dust can be easily scraped by the blade 905.
The toner scraped away by the blade 905 in the cleaning chamber 901 is transported to the toner storage 902 through a toner transportation port 908 disposed below the separator plate 903 by means of a rotative transportation paddle 907 with an L-shaped cross section disposed beside the cleaning roller 906.
However, the cleaning chamber 901 accommodating the cleaning roller 906 and transportation paddle 907 occupies a relatively large space in the cleaning unit, thereby reducing the relative volume of the toner storage 902. This means that the toner storage capacity relative to the entire size of the cleaning unit is reduced. In other words, the size of the cleaning unit has to be increased to ensure a required toner storage capacity.
In addition, the toner transportation from the cleaning chamber to the toner storage requires the transportation paddle and a driving mechanism for rotatably driving the transportation paddle, resulting in an increased production cost.
Further, if the accumulation level of the toner stored in the toner storage 902 exceeds the altitude of the lower end 903a of the separator plate 903 and the toner blocks the toner transportation port 908 as shown in FIG. 4, the aforesaid transportation paddle 907 is disabled from transporting the toner to the toner storage 902. Accordingly, the toner remains in the cleaning chamber 901, thereby causing a cleaning failure at an earlier stage.